Process of manufacturing portland cement from slag.



UNITED STATES PATENT OFFICE.

CARL VON FORELL, OF HAMBURG, GERMANY, ASSIGNOR TO HENRY EDMUNDS, OFLONDON, ENGLAND.

PROCESS OF MANUFACTURING PORTLAND CEMENT FROM SLAG.

Specification of Letters Patent.

Patented July 25, 1905.

Application filed December 29,1903. Serial No. 186,935.

To all whom, it may concern.-

Be it known that i, CARL VON FoRELL, a citizen of Germany, residing atHamburg, Germany, have invented new and useful Improvements in Processesfor the Manufacture of Portland Cement from Slag, of which the followingis a specification.

The production of Portland cement is well known according to the methodof burning water-granulated blast-furnace slag having a lime content offifty per cent. in a kiln to the clinkering-point, thereupon cooling it,and finally grinding it. I have found, however, that a good cement ofthe useful qualities of Portland cement may be obtained from suchblastfurnace slag if the watergranulated basic slag, which may be mixedwith usinemeal (slag-meal) and may be pressed into stones, is burnedwith an oxidizing-flame and is then subjected to a sudden dry cooling,while for the purpose of oxidation just before cooling small quantitiesof water may be added to the basic slag. By these means the slag obtainsa greater brittleness and crispness, by reason of which characteristicsthe slag may be more readily ground. Furthermore, in this manner theprocess of production is shortened, and it also results that air,carbonic acid, or moisture cannot decompose the cement into silica andlime, the hydraulic qualities of the cement, therefore, being bet terretained in consequence of the sudden cooling than with a slow coolingor a granulation in water.

According to later experiments the principal chemical factor in thesetting of the cement is the combination of silicic acid and lime, sothat when by reason of the access of air, carbonic acid, and moisturethe lime separates the conditions for the commencement of such chemicalcombination are disturbed and the hydraulic qualities of the cement arelessened.

in carrying out the new process it is advisable to proceed as follows:The burning of the slag should in order to obtain a uniform mixture takeplace in a rotary kiln from which the mass burned with anoxidizing-flame and issuing at the highest heat of the kiln isdisintegrated as thoroughly as possible and thrown as rapidly aspossible against intenselycooled dry surfaces. It is essential that thesudden cooling process and chilling follow at once and immediately afterthe burning process.

The result of the sudden cooling is that the hydraulic factors-lime,silica, and clay combinations-which are developed by the hightemperature retain their full energy and do not suffer a shifting of themolecules by taking up oxygen, carbonic acid, or moisture, nor does adisassociation of the combination which took place in the fire result,so that the chilled material only requires to be ground in order to forma finished cement.

What I claim is 1. The process of producing cement from furnace-slagwhich consists in forming briquets from a mixture of watergranulatedfurnace-slag and slag-meal, in roasting said briquets in a rotary kilnin an oxidizingflame, in adding to said highly-heated slag smallquantities of water, in disintegrating and projecting said heated slagagainst chilled surfaces, and in grinding said treated slag material.

2. The process of producing cement from furnace-slag which consists informing briquets from furnace-slag, in roasting said briquets, intreating said heated slag with small quantities of water, indisintegrating and projecting said heated slag into contact with coolingmeans and 'in grinding said treated slag.

3. The process of producing cement from furnace-slag which consists informing briquets of furnace-slag, in burning said briquets, indisintegrating and projecting said heated slag into contact with coolingmeans, and in grinding said treated slag.

4. The process of producing cement from furnace-slag which consists inburning watergranulated slag in a rotary kiln in an oxidizing-flame andin disintegrating and projecting said heated slag into contact withcooling means.

Signed by me at Hamburg this 18th day of December, 1903.

CARL VON FORELL. Witnesses:

F. POTHS, J. OHRIsT. HAFERMANN.

